Abstract :
μSR spectroscopy down to 40 mK was carried out on PrAu2Si2. This compound and heavy fermion URh2Ge2 are the only stoichiometric spin glasses reported among the tetragonal FT2X2 (F=rare earth or actinide, T=transition metal, X=metalloid) materials. Although bulk measurements on PrAu2Si2 exhibit all the typical features of a canonical spin glass with a freezing temperature of ∼3 K, no evidence for the formation of a frozen spin-glass state was found with μSR. Instead, the data clearly demonstrate that the magnetic moments in PrAu2Si2 remain dynamic down to the lowest temperatures. The discrepancy between these observed dynamics and the spin-glass-like response in bulk measurements is not understood. Analogous measurements on PrAu2Ge2 and PrAu2(Ge0.8Si0.2)2 showed the expected antiferromagnetic signals, demonstrating that in this type of alloy muons detect magnetic properties in the usual manner.
